With the rapid development of the display technology, the touch control display panel has been widely applied and accepted, used by the people. For example, the smart phone, the flat panel computer and etc. all use the touch control display panel. The touch control display panel is to combine the touch control panel and the liquid display panel as one to make the liquid crystal display panel equipped with functions of display and sensing the touch control inputs at the same time.
Generally, the liquid crystal panel mainly comprises a Color Filter (CF), a Thin Film Transistor Array Substrate (TFT Array Substrate) and a Liquid Crystal Layer positioned inbetween. The working principle is that the light of backlight module is reflected to generate images by applying driving voltages to the two glass substrate for controlling the rotations of the liquid crystal molecules. The formation process generally comprises: a forepart Array process, a middle Cell process and a post module assembly process. The forepart Array process is mainly to form a TFT substrate and a CF substrate; the middle Cell process is to laminate the TFT substrate and the CF substrate, and to inject liquid crystals between the two; the post module assembly process is to assemble the liquid crystal panel and the backlight module.
The touch control display panels can be categorized into four types of resistive, capacitive, optics, surface acoustic wave according to the sensing technology. At present, the main stream touch control technology is the capacitive type. According to the different structures of the touch display panels, the panels can be divided into: In Cell touch display panel and Out Cell touch display panel. The Out Cell touch display panel is to separately produce the touch panel and the liquid crystal display panel, and then to be laminated together to be a display panel having touch control function. The Out Cell has drawbacks of higher manufacture cost, lower light transmittance and thicker module. The In Cell touch display panel is to embed the touch panel function inside the liquid crystal panel to make the liquid crystal panel possess functions of display and touch input sense at the same time. In comparison with the Out Cell touch display panel, it has advantages of lower cost and thinner thickness, and has been favored by respective big display makers. Furthermore, according to the different positions of the touch circuit embedded in the liquid crystal panels, the In Cell touch display panels can be categorized into two types: one is that the touch control circuit is on the liquid crystal cell (On Cell), and the other is that the touch control circuit is inside the liquid crystal cell (In Cell). Compared with the Out Cell touch display panel, the In Cell touch display panel can make the panel lighter and thinner and has already been employed by a lot of mobile phone producers. It has been the main development direction of the future touch control technology.
For ensuring the normal work of the In Cell touch display panel, it is required to detect the embedded touch circuit. As shown in FIG. 1, which is a detection circuit of the In Cell touch display panel according to prior art, comprising a plurality of touch sensing electrodes 110 aligned in array and mutually insulated, and each touch sensing electrode 110 correspondingly coupled to one touch conductive line 120, and the touch conductive line 120 adjacent to the touch sensing electrode 110 is respectively coupled to the odd touch sensing electrode detection line 130 and even touch sensing electrode detection line 140 via detection switches 150. The touch sensing electrodes 110 are the common electrode (COM) of the liquid crystal display panel.
Specifically, as the In Cell touch display panel normally functions, the detection switch 150 is in off state, and all the touch sensing electrodes 110 are independent with one another. As conducting the function detection of the In Cell touch display panel, the detection switch 150 is in activation state. The low voltage corresponding to 0 gray scale is inputted to all the touch sensing electrodes 110 coupled to the odd touch sensing electrode detection line 130 via the odd touch sensing electrode detection line 130, and the high voltage corresponding to 255 gray scale is inputted to all the touch sensing electrodes 110 coupled to the even touch sensing electrode detection line 140 via the even touch sensing electrode detection line 140. Meanwhile, the high voltage corresponding to 255 gray scale is inputted to each pixel electrode (not shown) via the data signal line (not shown), and then watching the display condition of the panel. As shown in FIG. 2, if the voltage of the touch sensing electrode 11 is the white image of the low voltage corresponding to 0 gray scale, and the voltage of the touch sensing electrode 11 is the black image of the high voltage corresponding to 255 gray scale. Then, it shows that the touch function is normal; if the display image does not show according to the aforesaid rules, it shows that the function of the touch sensing electrode 110 is abnormal, and short circuit or disconnection might exist.
The aforesaid detection method of the In Cell touch display panel cannot execute detection after the Cell process is accomplished. Once function abnormity of the touch sensing electrode occurs, the array substrate and the color filter substrate are scrapped together. The cost of the Cell process is wasted, too.